Photographic processing apparatus with liquid level control

ABSTRACT

Photographic processing apparatus including an adjustable overflow conduit for varying the level of a bath of processing liquid and thus the effective processing time for the material, the conduit also including an outlet aperture adjacent the bottom of the liquid bath for discharging the liquid from the bath at a predetermined rate, the liquid from the overflow conduit emptying into a liquid reservoir from which the liquid is recirculated to the processing bath at a rate such that the amount of liquid discharged through the lower outlet opening makes up the bulk of the liquid being recirculated in order to create agitating currents along the bottom of the liquid bath.

Unite States Patent [7 2] Inventors Hans Kappeler;

Josef Christen, both of Zurich, Switzerland; Albert Petrus Wagemans, Edegem, Belgium [21 Appl. No. 807,529 [22] Filed Mar. 17, 1969 [45] Patented Dec. 14, 1971 [73] Assignee Gevaert-Agfa N.V.

Mortsel, Belgium [32] Priority Sept. 25, 1968 [33] Belgium [31 1 48,330

[54] PHOTOGRAPI-IIC PROCESSING APPARATUS WITH LIQUID LEVEL CONTROL 2 Claims, 3 Drawing Figs.

[52] US. Cl 95/89 R, 95/97, 1 18/429 [51 Int. Cl G03d 3/02 [50] Field of Search ..95/89, 89 L, 94, 97; 1 18/429; 355/10 [56] References Cited UNITED STATES PATENTS 1,987,387 1/1935 Conklin Primary Examiner-Samuel S. Matthews Assistant Examiner Robert P. Greiner Attorney-William J. Daniel ABSTRACT: Photographic processing apparatus including an adjustable overflow conduit for varying the level of a bath of processing liquid and thus the effective processing time for the material, the conduit also including an outlet aperture adjacent the bottom of the liquid bath for discharging the liquid from the bath at a predetermined rate, the liquid from the overflow conduit emptying into a liquid reservoir from which the liquid is recirculated to the processing bath at a rate such that the amount of liquid discharged through the lower outlet opening makes up the bulk of the liquid being recirculated in order to create agitating currents along the bottom of the liquid bath.

Patented Dec. 14, 1971 2 Sheets-Sheet 1 Patented Dec. 14, 1971 2 Sheets-Sheet Z PHOTOGRAPIIIC PROCESSING APPARATUS WITH LIQUID LEVEL CONTROL The present invention relates to a processing apparatus for photographic material, containing a tray with processing liquid, guide elements to guide at least one sheet of photographic material along a determined path through the processing liquid in the tray, and driving means for transporting the said photographic material at a constant speed through the processing apparatus.

Apparatus of the mentioned type are well known in the production of copies according to the silver halide process, the stabilization process, the silver complex diffusion transfer process, and other processes. According to all these processes an imagewise exposed light-sensitive material is made to contact a processing liquid for some time to make the latent image, which has been formed therein, visible or to make the latent image servicable in some other way.

The processing time in the mentioned apparatus determined by the speed at which the sheet to be treated is passed through the apparatus and by the effective processing length. By "effective processing length is meant hereinafter the distance of the path which is covered by the leading edge, or in general, by any point of the photographic material, up from the moment of contact with the processing liquid until the moment the processed material leaves the apparatus. Since the present invention is mainly concerned with types of apparatus in which the processing liquid is squeezed off from the surface of the sheets by a pressure roller pair when they leave the apparatus, the term effective processing length as used in the following description points to the distance of the path covered by a sheet when passing through the processing liquid, and increased by the distance of the path comprised between the point where the sheet leaves the processing liquid and the point where it is squeezed ofi' by the pressure roller.

For various reasons it is desired to modify the processing time. One reason is constituted by the difference in sensitivity of a material as a function of a determined processing liquid. As another reason it may be stated that an apparatus of the described type is, in principle, suited for performing various photographic copying methods wherein, however, various processing times have to be practiced. Finally, still another reason refers to differences in temperature of the processing liquid in case the temperature thereof is not thermostatically controlled or, if the temperature of the liquid is controlled indeed by a control device, the ambient temperatures exceed the adjustable maximum temperature of the device, such as may arrive under climatic conditions of the tropics.

As a first measure enabling the modification of the processing time the speed of the driving means of the apparatus may be adjustable. This measure has shown to be only partially successful then, for reasons of cost price, a discontinuously adjustable driving system, which has only a few driving speeds, is mostly applied.

According to another measure the guide members in the tray may be replaced by other guide members which determine a path of modified distance to be followed by the sheet of photographic material. This measure is little convenient in practice and moreover .it enables the performance of only a restricted adjustment.

The subject of the present invention is to provide a simple adjusting system which permits to modify the processing times of a sheet of photographic material within detennined limits.

The processing apparatus for photographic material according to the invention comprises a tray for processing liquid, guide members for guiding at least one sheet of photographic material along a determined path through the processing liquid in the tray, driving means for transporting the sheet of photographic material at a constant speed through the processing apparatus, an overflow device for maintaining in the tray the processing liquid, which is supplied by a pump arrangement from a reservoir to the tray, at a constant level, and wherein the overflow device is adjustable so that the level of the liquid in the tray may be modified.

According to a particular embodiment of the invention the overflow device is constituted by a vertical tube of square or rectangular cross section located in the tray, the underside of which communicates with the said reservoir for the processing liquid and one wall of which is provided with an opening which extends from the upper tube rim to at least the desired minimum level of the liquid in the tray, and wherein the vertical edges of the cutout wall are provided with grooves for the insertion of plates.

Although the apparatus according to the present invention has been mainly developed in connection with apparatus for performing the silver halide difiusion transfer process, it is however not limited to the particular process, but essentially applies to each photographic copying process wherein a sheet of photographic material is submitted to a treatment such as developing, fixing, etching, bleaching out, stabilizing, etc. during a detennined time.

The term "a sheet" as used in the present description must be understood in a broad way and aims at materials the dimensions of which may vary from small strips to webs of arbitrary length.

The term photographic material" applies to supports bearing layers in which a latent image can be formed under the influence of light, heat and other actinic radiation, supports onto which the image of an other support can be transferred, supports for constituting a printing master in the preparation of copies in a mechanical way.

The invention will be described hereinafter by way of example with reference to the accompanying drawings:

FIG. I is a perspective view of an apparatus for preparing an aluminum offset plate according to the silver complex diffusion transfer process.

FIG. 2 is a diagrammatic longitudinal section of the apparatus, and

FIG. 3 is a view in detail of the overflow device.

The apparatus as shown in FIGS. 1 and 2 is an apparatus for preparing an aluminum offset plate for use in an ofiset printing machine.

In the apparatus an imagewise exposed light-sensitive material, called hereinafter sheet 12 (the negative material) is treated with a processing liquid to bring about the development of the latent image and is then pressed against an imagereceiving layer, called hereinafter sheet 13 (the aluminum sheet). By the action of a solvent for the silver halide the unexposed silver complexes diffuse to the aluminum sheet where they are reduced to form a positive silver image of the original to which the negative sheet has been exposed.

The feed unit 11 comprises two horizontal support plates 14 and 15 which may be fixed to the housing 10 by means of triangular brackets 16 which are provided with hooks l7 and 18 which fit at each lateral side of the apparatus over studs 19 and 20. The upper support plate 14 is hingedly connected to the feed unit by means of hinges 21 and 22. In the closed position, as shown, the plate 14, rests with its front margin on the support blocks 23, 24 attached to the comer parts of the lower support plate 15. The upper support plate 14 carries a guide 25 which defines the lateral position of the sheet 12. The guide is continuously laterally adjustable by means of a mechanism sliding in the slot 26 and which may be locked by the locking knob 27. The lower support plate 15 has a guide 28 which defines the lateral position of the sheet 13. The said guide has two possible positions, the second being shown in broken lines, and is secured to the plate by means of a snap-fitting mechanism, not shown.

The processing zone in the apparatus is formed by a tray 30 shaped in longitudinal direction as shown in F IG. 2 and which is supported by a frame 36. Processing liquid is pumped by a small centrifugal pump 32 from a reservoir 31 to the tray 30 in which the liquid is flowed through an inlet opening 33 situated in a sidewall. The liquid in the tray is kept to a constant level by means of a vertical overflow pipe 34 which is located at the other sidewall of the tray and the underside of which fits to the inner bottom part of the tray 30. This overflow pipe is shown in detail in FIG. 3. It is formed by a plastic tube of square cross section and the front wall of which is provided with a rectangular opening. The sidewalls of the tube which are adjacent to the opening containing front wall, have grooves 51 and 52 respectively in which the plates 53 and 54 fit. At the bottom the tube 34 is provided with an opening 55 of determined sizes whereby it is secured that the quantity of liquid pumped per time unit by the pump 32 to the processing tray, is always greater than the quantity of liquid which can flow from the tube 34 through this opening and through the gaps left between the plates and the edges of the rectangular opening. ln this way always a small surplus of liquid will flow over the upper rim of the plate 53 into the tray so that the liquid in the tray will be kept to a rigorously constant level. The liquid flowing into the tube 34 passes through the opening 38 and the conduit 39 back to the reservoir 31.

The object of the opening 55 in the tube 34 is to create a rather intense current of the liquid mass contained in the tray. The surface current which is created by the overflowing of the plate 53 is of little service for the agitation of the liquid in the tray and therefore this current is kept small in respect of the current through opening 55.

The tray 30 is provided with laterally spaced ribs 40 which determine the path of the sheet 13 through the processing liquid. Guide plates 41 and 42 determine the path of the sheet 12 through the processing zone. The plates 41 and 42 are provided with a plurality of openings, not shown, for enabling the circulation of the processing liquid.

The transport of the sheets through the apparatus occurs by means of the roller pairs 43, 44 and 45, 46 which feed the sheet 12 of the sheet 13 respectively, through the processing zone, and by the roller pair 47, 48 which presses both sheets firmly together as they leave the processing zone. The driving of these roller pairs is done by an electric motor which is represented diagrammatically by the numeral 63. During the operation of the apparatus the roller pair 47, 48 is continuously rotating whereas the rotation of the roller pairs 43, 44 and 45, 46 is controlled by sensing devices which are responsive to the arrival of the leading edge of the sheets when these sheets are introduced into the apparatus so that a positioning of the sheets in exact register with each other is possible in the longitudinal direction. An apparatus for said exact registering of both sheets is described in particular in our U.K. Pat. application No. l9,889/68: Apparatus for use in diflusion transfer copying," filed on Apr. 26, 1968.

The apparatus according to the present invention operates as follows. The apparatus is provided with processing liquid suited for the processing of the desired photographic material and the necessary number of plates or, when required, only one plate of the required height, is inserted into the grooves 51 and 52 so that the processing liquid in the tray will reach a level which, considering the transport speed of the rollers and the distance of the paths, gives the required processing time.

By means of the main switch 82 the motor 63 driving the rollers and the motor driving the pump 32 is started. A pilot lamp built in the transparent lid of the main switch warns the operator that the apparatus is switched on. A second pilot lamp which is provided in the transparent lid 87 is controlled by a floater element which is located in the reservoir 31 so that the lamp starts burning when the level of the liquid in the reservoir 31 falls under a determined minimum height so that a sufficient liquid supply to the tray 30 is no longer secured.

By means of the feed unit 11 the sheets 12 and 13 are slid into the apparatus. Both sheets travel along separated paths through the processing zone in a well-determined time and are then firmly pressed to each other by the rollers 47, 48 thereby starting the diffusion transfer. After the sheets have been nonimage parts of the obtained master. Then the aluminum printing master is treated with a lacquer composition to improve the mechanical resistance of the image.

The following table illustrates the modifications in the effective processing length of the negative sheet and the aluminum sheet, which are obtained at different levels of the processing liquid in the described device.

wherein:

H is the overflow height in the centimeter up from the lower rim 56 of the opening in the tube 34,

l.., is the effective processing length in centimeter of the negative sheet, and

L is the effective processing length in centimeter of the aluminum sheet.

The different heights H were obtained by various combinations of the three plates with a height of 0.5-1 and 2 cm., respectively.

The height of each plate can be indicated directly on the concerning plate itself. Occasionally, also other indications may be marked on the plates. For example, a plate may be directly provided with the name or the trademark of a determined material which can be treated with the liquid level imposed by the plate. lf wanted, a number of plates of different height can also be provided with different indications of temperature, etc.

The overflow system of the apparatus according to the present invention is not limited to the described embodiment. in a modified embodiment of the adjustable overflow conduit may be formed by a vertical cylindrical tube provided with a displaceable mufi and the upper rim of which determines the liquid level.

According to a further modified embodiment the conduit can be formed by a flexible or tippable tube with an upper rim the vertical position of which changes as a function of the tube inclination.

What we claim is:

1. Processing apparatus for photographic material comprising a tray for processing liquid; guide members for guiding at least one sheet of photographic material along a determined path through the processing liquid in the tray; driving means for transporting the sheet of photographic material at a uniform speed through the processing apparatus; and overflow conduit extending substantially vertically in said tray, a wall of the conduit having an opening therein extending partially around the conduit circumference, the height of said opening being at least equal to the difference between the desired minimum and maximum level of the liquid in the tray; and adjustable closure means to close this opening to a variable height between said levels.

2. Processing apparatus according to claim 1 wherein said conduit consists of a tube of quadrilateral cross section, one wall of which is provided with an opening extending from the upper tube rim to at least the desired minimum level of the liquid in the tray, the vertical edges of the wall opening being provided with grooves for the insertion of plates therein, and said closure means comprises a plurality of plates for insertion in the grooved edges of said opening to vary the height of the lower edge of said opening.

4: 1- m s m 

1. Processing apparatus for photographic material comprising a tray for processing liquid; guide members for guiding at least one sheet of photographic material along a determined path through the processing liquid in the tray; driving means for transporting the sheet of photographic material at a uniform speed through the processing apparatus; and overflow conduit extending substantially vertically in said tray, a wall of the conduit having an opening therein extending partially around the conduit circumference, the height of said opening being at least equal to the difference between the desired minimum and maximum levels of the liquid in the tray; and adjustable closure means to close this opening to a variable height between said levels.
 2. Processing apparatus according to claim 1 wherein said conduit consists of a tube of quadrilateral cross section, one wall of which is provided with an opening extending from the upper tube rim to at least the desired minimum level of the liquid in the tray, the vertical edges of the wall opening being provided with grooves for the insertion of plates therein, and said closure means comprises a plurality of plates for insertion in the grooved edges of said opening to vary the height of the lower edge of said opening. 